The present invention relates to a lubricating oil composition having improved temperature characteristics. More particularly, it is concerned with a lubricating oil composition which can maintain a constant viscosity at high temperatures and even at extremely low temperatures, is low in viscosity and further is excellent in properties such as shear stability, extreme pressure properties, wear resistance, detergency, dispersancy and so on. Therefore, this lubricating oil composition can be used in various applications, for example, as a multi-grade gear oil and a multi-grade engine oil. 2. Description of the Prior Art
Heretofore, in order to improve temperature characteristics of a lubricating oil, a large amount of a polymer compound acting as a viscosity index improver and/or a pour point depressant has been blended thereto.
Lubricating oil compositions thus prepared, however, have disadvantages in that shear stability is poor, viscosity is readily decreased by mechanical shear, and initial lubricating properties are not satisfied, because they contain a large amount of polymer compounds. Not only in this shear stability but also in extreme pressure properties, wear resistance, detergency, dispersancy and so forth, the above lubricating oil compositions are not satisfactory for practical use.